Thermal die marker



g- 19, 1969' P. VILLERS ETAL. 3,461,567

THERMAL DIE MARKER Filed Aug. 9, 1966 INVENTOR WOODROW L HAYES PHILIPPE VILLERS BY GM ATTORNEY and United States Patent 3,461,567 THERMAL DIE MARKER Philippe Villers, Vestal, and Woodrow L. Hayes, Binghamton, N.Y., assignors to Singer-General Precision, Inc., a corporation of Delaware Filed Aug. 9, 1966, Ser. No. 571,277 Int. Cl. 1126f 1/32; B23q 35/02; B231) 49/02 US. Cl. 33--189 3 tClaims ABSTRACT OF THE DISCLOSURE A heated die for marking thermoplastic materials having a working face from which extend marking elements consisting of a projection having a flat end surface and a sharp-edged annulus circumscribing the projection. Means are provided for rapid heating and cooling of the die.

This invention relates to devices for marking flat surfaces for ready subsequent identification, and, more particularly, to improved means for marking desired points on aerial photographs and the like while preserving as much information as possible on the photograph.

A composite photograph of a large area viewed from the air is generally formed from a plurality of separate exposures arranged in mosaic form. These separate photographs usually have overlapping portions even though they may be made by separate cameras in different aircraft. In order to properly arrange the mosaic to produce a single composite picture, the same objects shown on the several photographs must be identified and marked so that the several prints can be properly aligned. One of the earlier methods for marking the prints for later identification was by drilling a small hole in the emulsion. This small hole could be formed by means of a spade drill. Or, a steel ball was often impressed upon the emulsion to form a small dent therein. In both cases, the identifying mark was subject to being lost because the emulsion very often was self-healing. To overcome this disadvantage, heated steel die markers are being used to make permanent marks in the photographic emulsion. These steel dies generally comprise a pair of concentric rings which are heated. Each ring has what amounts to a knife edge which, when heated, is forced into the melting emulsion on the photographic film. The heated rings force the softened emulsion upward and outward in a pair of furrows, one on each side of the knife edge. The furrows are very similar to those formed by a plow. Unfortunately, the inner ring of the die is sufiiciently small so that the furrows formed by this inner ring meet, or substantially meet, in the center of the mark and destroy whatever information was contained therein, and, usually, this is the critical information to be identified.

It is an object of this invention to provide new and improved means for marking flat surfaces.

It is another object of this invention to provide a new and improved device for marking flat surfaces such as photographic film without destroying any more information than is necessary.

It is a further object of this invention to provide a new and improved die marker for creating distinctive marks on the surfaces of fiat sheets.

It is still another object of this invention to provide a new and improved heated die marker for use in distinctively marking desired locations on photographic film while leaving intact as much information as possible.

Other objects and advantages of this invention will become apparent as the following description proceeds, which description should be considered together with the accompanying drawings, in which:

FIG. 1 is a side view of a typical machine used in marking photographic film;

FIG. 2 is a perspective view of a prior art die marker used in the machine of FIG. 1;

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a perspective view of a new die marker according to this invention; and

FIG. 5 is a sectional view taken along line V-V of FIG. 4.

Referring now to the drawings in detail and FIG. 1 in particular, the reference character 11 generally designates a machine for marking flat surfaces such as the emulsions of aerial photographs. The marking machine 11 comprises a base 6 which supports a frame 9. A film positioner 8 is carried on the base 6, and, in turn, supports a fiat film 7. The frame 9 carries a ball bushing 14 which supports and guides a holder 12, and the holder 12 carries a die member 10 at one end. An electrical cable 28 supplies electrical energy from a power supply 26 to the die 16 through the holder 12, and a flexible chain 22 connects the holder 12 to a vertical movable member 19 which is slidably supported in a vertical guide Zll mounted on an arm of the frame 9. A horizontal shaft 18, which is connected to the vertical movable member 19 which is slidably supported in 21 end. A motor 13 is supported on the frame 9 and has an output shaft 15 to the end of which is fastened a truncated cam 16.

In operation, the marking machine 11 operates to mark appropriate locations on photographic emulsions at desired locations. Although not shown in detail, the positioner 8 includes means for manually or electrically moving the emulsion 7 in a horizontal plane to accurately position the desired spots on the film under the die 10'. This means may include high precision lead screws mounted at right angles to each other and carrying the main positioner 8. The positioner 8 should be operable to accurately locate points on the film 7 directly under the die member 11), which accuracy can then be measured in microns. The die member 10 in the holder 12 is electrically energized through the cable 28 from the power supply 26 so that the die 10 is quickly raised to a temperature suflicient to soften the emulsion 7 when the die is applied to the emulsion under a slight pressure. By supplying the electrical energy in pulses, the die 10 heats quickly and cools quickly to permit marking and then quick withdrawal.

When a spot on the film 7 is to be marked, the motor 13, the shaft 15, and the cam 16 make one complete revolution so that the cam follower 17, which rides along the surface of the cam 16, move downwardly as the upper surface of the cam 16 also moves downwardly. The cam 16 is shaped so that it has a flattened portion of much smaller radius than the remainder of the cam. As the cam 16 rotates and its flattened portion reaches a top position, the cam follower 17, the shaft 18, the vertical movable member 19, and the holder 12 move downwardly until the die 11) rests upon the emulsion 7. This equipment remains in this position so long as the flattened portion of the cam 16 remains in contact with the cam follower 17. As the cam 16 continues to rotate, the cam follower 17 is driven upwardly by the rising surface of the cam 16 to withdraw the die member 11) from the emulsion 7.

However, during the time that the die member 10 is supported upon the emulsion 7, the heat from the die member 10 softens the emulsion 7 and the weight of the holder 12 upon the die member 10 forces the sharp edges of the die into the emulsion 7 to provide a permanent mark therein. Most emulsions are thermo-plastic, and before the die member 10 is withdrawn, the emulsion 7 is permitted to cool and set in its newly deformed condition permitting ready withdrawal of the die without distortion of the mark. This provides a small mark which is accurately positioned and which is permanent on the surface of the film 7 so that the marked location can be easily identified later. Apparatus similar to that of FIG. 1 is described and illustrated in somewhat greater detail in Patent 3,205,587 issued on Sept. 14, 1965, to Richard F. Kilburn, and reference thereto may be made to additional details.

FIG. 2 is an enlarged illustration of an old die member 10. The die member 10 comprises a generally cylindrical shaft 31 which has a tapered portion 32 at its bottom end. The tapered portion 32 ends in a flat surface 37 from which projects a knife edge 33 forming a raised ring on the flat end 37 and defining within it a generally cylindrical depression 34. Centrally located and rising out of the depression 34 is a cylindrical member 35 having a central hole 36 to define a second knife edge. The knife edge formed by the member 35 and the knife edge 33 are concentric and must lie in the same plane. Although the knife edges shown in FIG. 2 are generally cylindrical in shape, other geometrical shapes may be used to form distinctive marks.

FIG. 3 shows the old die member 10 in section.

The two sharp edges of the die member 10 shown in FIGS. 2 and 3 produce a distinctive mark when used on photographic film. The use of sharp edges ensures a clear and sharp impression in the emulsion with very little pressure. However, there are several disadvantages in using the die member shown in FIGS. 2 and 3. The knife edge 33, even though small, is usually of a diameter such that its surface area is sufficiently large that the unit pressure is small. Thus, even though such knife edges are subject to rapid breakage and deterioration, this is not necessarily a major objection in the larger diameter knife edge 33, but becomes serious in the small diameter ring as. Also, the displaced emulsion from the groove formed by the knife edge 33 forms fur-rows on either side of that knife edge and of the subsequent mark. The diameter of the knife edge 33 is sufiiciently large that a substantial amount of the information within the ring formed by that knife edge 33 remains undestroyed and readily available. However, the inner projection 35 has such a small diameter that it is subject to rapid deterioration and inadvertent breakage. In addition, the diameter of the depression 36 is sufficiently small so that when the die 10 of FIGS. 2 and 3 is used to mark a photographic emulsion, the emulsion which is displaced by the projection 35 fills the central cavity 36 and completely destroys the information contained within the area of the projection 35. This is a serious defect which must be taken into consideration whenever such devices are used.

The die member 10 shown in FIGS. 2 and 3 has several serious disadvantages which have plagued it since it was first used. Because the rings 33 and 35 are thin, they are fragile, particularly the inner ring 35. Also, even if the rings do not break in use, they quickly wear out because they are thin. And, the die member 10 shown in FIG. 2 is expensive to manufacture. The inner ring 35 is in the order of 30 microns in diameter, and it is quite diflicult to form with a knife edge. In addition, the tops of the two rings 33 and 35 must be in the same plane, and this adds immeasurably to the difiiculty in manufacturing the die 10. Thus, the die 13 is very expensive to make in the first place, and after it is made it is fragile in the second place, and if it does not break first, it wears out quite quickly in the third place. This invention eliminates the above three disadvantages while providing, in addition, a die marker which works well and does not obliterate the information it is to mark for later identification.

An improved version of the die marker It is shown in FIGS. 4 and 5. The improved marker 40 comprises a main body portion 41 which may be cylindrical or any other convenient shape. The marker portion may be ta- .pered as shown at 42, and carries on its working end face 49 a ring 43 which may have a knife edge. This ring 43 surrounds a valley 44 out of which rises a projection 45 which may be centrally located. The die member 40 is split longitudinally into two parts 51 and 52 which are joined at one end by a narrow strip of metal 53 surrounding the ring 43 and the projection 45. The split 47 is partially filled with an electrically insulating material 48 such as an epoxy resin to add to the rigidity of the overall device, leaving sufiicient air space at the end to permit expansion of the bridge 53 and bending of the legs 51 and 52. As better shown in FIG. 5, the projection 45 has a flat surface 46 which is co-planer with the ring 43.

The die marker 4% as shown in FIGS. 4 and 5 presents many advantages over the prior art devices. For example, the marker 40 is not difficult to manufacture. The outer ring 43 and the projection 45 may be formed in any suitable manner, and they are then ground, or otherwise finished, to the same plane. This can be done quickly and with extreme accuracy. Since the projection 45 is provided with a flat surface 46, it has substantial strength and is not very fragile. In addition, the top surface of the outer ring 43 need not be particularly sharp and this, also, has substantial strength. In fact, there are situations where the outer ring 43 could be eliminated entirely. The die marker 40 is simply and readily heated by applying to the two legs, or conductors, 51 and 52 a pulsed electrical current from a suitable source such as a welding supply. In the marking apparatus shown in FIG. 1, the source is represented by power supply 26 which is electrically connected to legs 51 and 52 by conductors of cable 28 which extend through die holder 12. The two legs 51 and 52 comprise conductors having substantial cross-section which will readily conduct high density electrical currents without appreciable loss. However, the metal portion 53, which connects together the two legs 51 and 52, has a much smaller cross-sectional area than either of the two legs, and has, consequently, much higher resistance. Thus, the high density electrical currents flowing through the two legs 51 and 52 and through the connecting bridge 53 cause the connecting bridge 53 to heat quite rapidly to the desired marking temperature. When a pulse of electricity is supplied from the power supply, such as that shown at 26 in FIG. 1, the electrical pulse causes the marker portion including the ring 43 and the projection 45 to rapidly heat. If the marker portion is in contact with a photographic film emulsion, or other thermo-plastic film, the film adjacent the heated portion is rapidly softened. With a small amount of pressure applied to the marker 40, the ring 43 displaces the softened thermoplastic material and creates a depression with furrows formed on either side. However, because of the flattened surface 46 of the projection 45, the projection 45 throws furrows only on one side and creates a dent in the film within its area of contact, therefore not destroying the information within that area. Since the electrical pulse which heated the marker portion has a short duration, the heating of the ring 43 and the projection 45 occupies only a very short interval of time. As soon as the pulse decays, the heat from the end of the marker 40 is withdrawn by the legs 51 and 52 and rapidly cools the ring 43 and the projection 45 as well as the film which is being marked. Thus, before the marker 40 is withdrawn, the distorted film is cooled and remains in its distorted condition. This overcomes the disadvantages of the impressed steel balls which had been used in the past and whose impressions were self-healing. In addition, since the central area of the inner mark is unaffected by the projection 45, the information in this area is not destroyed.

The above specification has described and illustrated a new and improved die marker to uniquely mark fiat surfaces, such as those of photographic films and the like. This device has particular utility in aerial photography and similar systems where a mosaic is formed from a plurality of overlapping members. It is realized the above description may indicate to others who are skilled in this art additional ways in which the principles of this invention may be used without departing from their spirit. It is, therefore, intended that the above invention shall be limited only by the scope of the appended claims.

What is claimed is:

1. A photogrammetric marking device for placing a permanent index mark on the surface of a photographic emulsion, said device comprising, in combination:

(a) support means for holding the photograph to be marked;

(b) a marking member including a pair of separate leg portions joined at one end of each by a bridge portion;

(c) a projection extending from said bridge portion toward said support means;

(d) a flat end surface on said projection;

(e) means for moving said marking member toward and away from said support means along a predetermined path in such a way that said end surface of said projection contacts and indents a selected portion of the image surface of a photograph held on said support means;

(f) said means for moving being so constructed and arranged that said end surface is maintained substantially parallel to the surface of the photograph for at least that portion of movement of said marking member when said end surface contacts said photograph; and

(g) means for applying heat to said projection to cause said end surface to reach a temperature within a predetermined range during contact thereof with the surface of the photograph.

2. The device of claim 1 wherein said leg portions,

bridge portion and projection comprise electrical conductors, said leg portions being electrically insulated from one another, and said bridge portion has a smaller cross sectional area than said leg portions.

3. The device of claim 2 wherein said means for applying heat comprise a source of pulsed electrical energy, and means for applying electrical pulses from said source to said leg portions.

References Cited UNITED STATES PATENTS 25 EDGAR S. BURR, Primary Examiner U.S. Cl. X.R. 

